The present invention relates to an assembly for supporting and guiding a movable member of a machine for movement along an axis, particularly for a measuring machine.
Measuring machines are known which include a fixed base, a plurality of members movable along respective coordinate axes relative to the base and a tracer point adapted to be moved by the movable members along these axes.
In a typical configuration, the movable members consist of a portal movable relative to the base along a first horizontal axis (X) and having a cross-member extending along a second horizontal axis (Y) perpendicular to the first, a carriage carried by the portal and slidable on the cross-member along the Y axis, and a head carried by the carriage and movable relative thereto along a vertical axis (Z); the tracer point being fixed to the head in use.
In known machines of the type described briefly above, the portal is fixed to the base by a support and guide assembly including a plurality of flat slide surfaces formed on the base and extending parallel to the X axis and respective bearing pads, for example of the pneumatic type, fixed to the portal and arranged to slide on these surfaces. The arrangement of the slide surfaces and of the respective bearing pads is such as to prevent the portal from moving in the Y and Z directions; for this purpose, two slide surfaces are generally provided extending perpendicular to the Y axis and on which respective bearing pads act in opposition to each other so as to bear the loads acting in the two directions along the Y axis; similarly, two slide surfaces are provided perpendicular to the Z axis on which respective bearing pads act which oppose each other so as to bear the loads acting in the two directions along the Z axis.
This configuration, although being satisfactory from the point of view of performance, has the disadvantage of being rather expensive. This expense is due to the use of a large number of bearing pads and to the mechanical working of the four tracks which must be such as to ensure that their dimensions are extremely precise and they have a high quality finish.